DAWN ENHANCEMENT OF AURORAL EMISSION

Abstract

The 0–0 band at 3914 Å was observed once per minute with a scanning spectrometer as sunlight illuminated the upper atmosphere on the morning of September 5, 1958. It is reasonable to assume that the density of [Formula: see text] ions was maintained constant during this time, and that the observed rise of intensity was due to resonance scattering of sunlight. The ions were found to be distributed between 180 and 320 km with peak at 250; density here was 12 × 10⁴ ions/cm³. There was some evidence for another layer at 120 km. Rotational temperatures measured while the main layer was fully illuminated agreed well and gave an average of 1060 ± 100 °K.